In the case of such circuit arrangements, it is necessary to produce pneumatic pulsations for the control of double-acting operating cylinders at certain, adjustable periodic time intervals. For this purpose, there are certain presently known control systems for effecting periodic operation of fluid pressure windshield-wiper drives, for example, which include a piston motor, a reversing valve for alternating the air pressure on the double piston of the motor, and an operating valve for connecting and disconnecting the reversing valve with or from a fluid pressure source, in which case the periodic operation is controlled as a function of the length of travel of the wiper.
Disadvantages experienced with these known windshield-wiper drives with periodic operation are the starting and reversing difficulties at the end of travel position as in the case of a relatively small wiping angle, for instance, caused by compressed snow accumulations on the windshield of a vehicle.